1. Field of the Invention
The present invention relates to a liquid-crystal projection device i.e. what is known as a projector and in particular relates to improvements in the light source and peripheral optical system of a small-size liquid-crystal projection device.
2. Description of the Relate Art
As the light sources employed in conventional liquid-crystal projection devices, light sources using a fluorescent tube or light-guide plate or electrical discharge-type light sources such as metal halide lamps have come to be employed.
In particular, Japanese Patent Laid-Open number Sho.51-119243 discloses a flat plate-shaped light source. This specification states that the flat plate-shaped light source employs electroluminescence i.e. electroluminescent elements.
However, in the case of a light source employing a fluorescent tube or light-guide plate, it is difficult to make the diameter of the fluorescent tube etc. small. There was therefore the problem that miniaturization of a liquid-crystal projection device was difficult, since the thickness of the light source itself could not be reduced below the diameter of the fluorescent tube.
Also, in the case of an electric discharge-type light source such as a metal halide lamp, the reflector of large aperture that was considered necessary to direct the light diverging from the light source parallel to the liquid crystal panel was a factor impeding miniaturisation of the liquid-crystal projection device.
In particular in the came of a liquid-crystal projection device for colour display, further miniaturisation of the liquid-crystal projection device was difficult owing to the need to provide liquid crystal display elements consisting of a light source as aforementioned and liquid crystal panel for each of the primary colours constituting the colour image.
Also, Japanese Patent Laid-Open number Sho.51-119243 does not clearly disclose a material constituting a luminescent layer of an electroluminescent element. When the conventional inorganic electroluminescent material is employed as material for this luminescent layer, light from the electroluminescent element in light of a highly divergent character. This therefore suffered from the problem that projection of a bright image could not be achieved since the light could not be effectively directed into the aperture of the projection lens.
A further problem was that the drive voltage required for an electroluminescent element using inorganic material is at least 100 volts, which is comparatively high.
An object of the present invention is to provide a liquid-crystal projection device wherein, in order to solve the above problems, greater miniaturisation than conventionally can be achieved and in which a bright image can be projected with low voltage.
In more detail, a first task of the present invention is to provide a miniature liquid-crystal projection device that can be driven with lower voltage than conventionally and whereby a brighter image than conventionally can be projected by preventing the diminution in the amount of light produced by divergence of the light, by employing an organic electroluminescent element having a resonator structure whereby light of good optical emission directionality is emitted.
A second task of the present invention is to provide a miniature liquid-crystal projection device whereby a brighter image than conventionally can be projected by increasing the amount of light that can be transmitted through the polarizing plate of the liquid crystal panel by using a polarization conversion element that can convert the condition of polarization of the emitted light from the light source.
A third task of the present invention is to provide a miniature liquid-crystal projection device whereby a brighter image than conventionally can be projected, by increasing the amount of light that can be transmitted through the polarizing plate of the liquid crystal panel by employing a polarisation conversion element that functions in a specified wavelength band in projecting a colour image.
A fourth task of the present invention is to provide a miniature liquid-crystal projection device whereby a brighter image than conventionally can be projected by increasing the amount of light that can be transmitted through the aperture of a pixel and miniaturising the device itself by employing a miniature luminescent element comprising a microlens array element that focuses the light on to pixel apertures of the liquid crystal panel.
A fifth task of the present invention is to provide a miniature liquid-crystal projection device whereby a clear image can be projected by raising the purity of the light that is projected and the brightness compared with conventionally, by increasing the amount of light consisting of light of only a specified wavelength by employing miniature lumuinescent elements that emit light of only a specified wavelength, due to optical resonance, in projection of a colour image.
A liquid-crystal projection device according to claim 1 consists in a liquid-crystal projection device having a liquid crystal display element comprising: an organic electroluminescent element constructed by sandwiching an organic thin-film element between an electrode layer that reflects light and an electrode layer that transmits light; and a transparent liquid crystal panel that controls the transmission of light emitted from a face of the organic electroluminescent element.
A liquid-crystal projection device according to claim 2 consists in a liquid-crystal projection device according to claim 1 wherein the organic thin-film layer is constituted as a white luminescent layer that emits white light.
A liquid-crystal projection device according to claim 3 consists in a liquid-crystal projection device according to claim 1 wherein the organic thin-film layer is constituted by successively stacking primary colour luminescent layers that respectively emit light of respective wavelength regions of a plurality of primary colours necessary for colour display.
A liquid-crystal projection device according to claim 4 consists in a liquid-crystal projection device according to claim 1 wherein the organic electroluninescent element in constituted of a transparent electrode layer overlying a transparent substrate, the organic thin-film layer overlying this transparent electrode layer and an electrode layer overlying the organic thin-film layer and that reflects light emitted by the organic thin-film layer.
A liquid-crystal projection device according to claim 5 consists in a liquid-crystal projection device according to claim 1 wherein the organic electroluminescent element comprises: an electrode layer that reflects light emitted from the organic thin-film layer; a transparent electrode layer that sandwiches the organic thin-film layer between itself and this electrode layer; and a half-mirror layer provided on the optical output side from this transparent electrode layer and that reflects some of the incoming light through the transparent electrode layer into the electrode layer, while transmitting the rest of this light; and the distance between this half-mirror layer and the electrode layer is set to an optical distance that produces resonance of the light in question.
A liquid-crystal projection device according to claim 6 consists in a liquid-crystal projection device according to any one of claims 1 to 5 wherein, between the organic electroluminescent element and the transparent liquid crystal panel there is further provided a polarization conversion element that converts the polarization condition of emitted light from the organic electroluimnescent element, and the transparent liquid crystal panel is provided with a polarizing plate that transmits light of specified polarization condition, of the light emitted after passing through the polarization conversion element.
A liquid-crystal projection device according to claim 7 consists in a liquid-crystal projection device according to claim 6 wherein the polarization conversion element comprises: a circular polarization selective reflection filter arranged on the organic electroluminescent element side and that reflects one circularly polarized component of right-handed circularly polarized light and left-handed circularly polarized light and that transmits the other circularly polarized component, and a xc2xc wavelength plate that converts circularly polarized light to linearly polarized light and that converts linearly polarized light to circularly polarized light.
A liquid-crystal projection device according to claim 8 consists in a liquid-crystal projection device according to claim 6 wherein the polarization conversion element comprises: a linearly polarized light selective reflection filter arranged on the transparent liquid crystal panel side and that, of two perpendicular linearly polarized components, reflects one linearly polarized component and transmits the other linearly polarized component, and a xc2xc wavelength plate that converts circularly polarized light into linearly polarized light and that converts linearly polarized light into circularly polarized light.
A liquid-crystal projection device according to claim 9 consists in a liquid-crystal projection device according to any of claims 6 to 8 wherein the polarization conversion element comprises a polarization selective reflection filter that, for the emitted light of a specified wavelength region, transmits light of this specified polarisation condition and reflects light o: other polarization conditions.
A liquid-crystal projection device according to claim 10 consists in a liquid-crystal projection device according to claim 6 wherein, between the organic electroluminescent element and the transparent liquid crystal panel, there is further provided a front-side microlens array element wherein microlens elements that collect output light from the organic electroluminescent element are arranged corresponding to individual pixels of the transparent liquid crystal panel.
A liquid-crystal projection device according to claim 11 consists in a liquid-crystal projection device according to claim 10 wherein the focal length of the microlens elements and the distance between the front-side microlens array element and this liquid crystal panel are adjusted such that the apertures of the individual pixels of the transparent liquid crystal panel are arranged in the vicinity of the rear-side focal point of the microlens elements.
A liquid-crystal projection device according to claim 12 consists in a liquid-crystal projection device according to any of claims 10 or 11 wherein the transparent liquid crystal panel comprises an optical screening element that transmits light that is incident on the aperture of each pixel and that screens light that in incident on portions other than the aperture of this pixel.
A liquid-crystal projection device according to claim 13 consists in a liquid-crystal projection device according to any of claims 10 to 12, further comprising a rear-side microlens array element constituted by arranging, corresponding to individual pixels, microlens elements that suppress divergence of light transmitted through the pixel apertures of the liquid crystal panel, on the side where light is output after passing through the transparent liquid crystal panel.
A liquid-crystal projection device according to claim 14 consists in a liquid-crystal projection device according to claim 13 wherein the focal length of the microlens elements and the distance between this rear-side microlens array element and this transparent liquid crystal panel are adjusted such that the apertures of the pixels are arranged in the vicinity of the front-side focal point of the rear-side microlens elements.
A liquid-crystal projection device according to claim 15 consists in a liquid-crystal projection device according to any of claims 10 to 14 wherein, between the organic electroluminescent element and the front-side microlens array element, there in further provided a polarization conversion element that converts the polarization condition of light that is output from the organic electroluminescent element, and the transparent liquid crystal panel comprises a polarizing plate that transmits light of specified polarization condition, of the light that is output after passing through the polarization conversion element.
A liquid-crystal projection device according to claim 16 consists in a liquid-crystal projection device according to claim 15 wherein the polarization conversion element comprises a circular polarization selective reflection filter arranged on the organic electroluminescent element side and that reflects one circularly polarized component of right-handed circularly polarized light and left-handed circularly polarised light and that transmits the other circularly polarized component, and a xc2xc wavelength plate that converts circularly polarized light into linearly polarized light and that converts linearly polarized light into circularly polarised light.
A liquid-crystal projection device according to claim 17 consists in a liquid-crystal projection device according to claim 15 wherein the polarization conversion element comprises. a linear polarization selective reflection filter arranged on the front-side microlens array element side and that, of two perpendicular linear polarization components, reflects one linearly polarised component and transmits the other linearly polarized component, and a xc2xc wavelength plate that converts circularly polarized light into linearly polarized light and that converts linearly polarized light into circularly polarized light.
A liquid-crystal projection device according to claim 18 consists in a liquid-crystal projection device according to any of claims 1, 4 or 5, further provided with a projection lens that projects on to a screen an image generated by passing through the transparent liquid crystal panel.
A liquid-crystal projection device according to claim 19 consists in a liquid-crystal projection device according to claim 18 further provided with a transparent screen whereby an image projected from the projection lens can be observed from the opposite side of this projection lens.
A liquid-crystal projection device according to claim 20 consists in a liquid-crystal projection device according to any of claim 1 or claim 4, further provided with a plurality of liquid crystal display elements that control the transmission of light of respective wavelength regions of a plurality of primary colours necessary for colour display; a combining optical system that generates a colour image by combining images of primary colours emitted from the plurality of liquid crystal display elements; and a projection lens that projects on to a screen a colour image combined by the combining optical system.
A liquid-crystal projection device according to claim 21 consists in a liquid-crystal projection device according to claim 20 wherein the plurality of organic electroluminescent elements are provided with an optical resonant structure.
A liquid-crystal projection device according to claim 22 consists in a liquid-crystal projection device comprising, for each primary colour, liquid crystal display elements including organic electroluminescent elements having an optical resonant structure adjusted such an to emit light of respective wavelength regions of a plurality of primary colours necessary for colour display and a transparent liquid crystal panel that controls the transmission of light emitted from the face of the organic electroluminescent elements; and further comprising a combining optical system that generates a colour image by combining images of each primary colour emitted from the respective liquid crystal display elements, and a projection lens that projects on to a screen the colour image combined by the combining optical system.
A liquid-crystal projection device according to claim 23 consists in a liquid-crystal projection device according to any of claims 20 to 22 further comprising a transparent screen constituted so that an image projected from the projection lens can be observed from the opposite side of this projection lens.
A liquid-crystal projection device according to claim 24 consists in a liquid-crystal projection device according to any of claims 20 to 23 wherein the liquid crystal display elements further comprise, between the organic electroluminescent element and the transparent liquid crystal panel, a front-side microlens array constituted by arranging, corresponding to individual pixels of the transparent liquid crystal panel, microlens elements that collect the light emitted from the organic electroluminescent element.
A liquid-crystal projection device according to claim 25 consists in a liquid-crystal projection device according to claim 24 wherein the liquid crystal display elements further comprise a rear-side microlens array element constituted by arranging, corresponding to each pixel, microlens elements that suppress divergence of light passing through the pixel apertures of the liquid crystal panel, on the output side of light that has passed through the transparent liquid crystal panel.
A liquid-crystal projection device according to claim 26 consists in a liquid-crystal projection device according to any of claims 24 or 25 wherein the front-side microlens array element and the rear-side microlens array element of the liquid crystal display elements comprise a reflection preventing film adjusted such that its reflectivity is lowest for light of the wavelength region of the primary colour allocated to the liquid crystal display element in question.
A liquid-crystal projection device according to claim 27 consists in a liquid-crystal projection device according to any of claims 20 to 26 wherein the liquid crystal display elements, between the organic electroluminescent element and the front-side microlens array element, are further provided with a polarization conversion element that converts the polarisation condition of emitted light, from the organic electroluminescent element, and the transparent liquid crystal panel is provided with a polarizing plate that transmits light of specified polarization condition of light that is emitted after having passed through the polarization conversion element.
A liquid-crystal projection device according to claim 28 consists in a liquid-crystal projection device according to claim 27 wherein the polarization conversion element of the liquid crystal display elements comprises a polarization selective reflection filter that transmits light of specified polarization condition with respect to the emitted light of a specified wavelength region and that reflects light of polarization condition other than this.